Switching the regioselectivity in the copper-catalyzed synthesis of iodoimidazo[1,2-a]pyridines.

A unique copper-catalyzed binucleophilic switching of 2-aminopyridine has been developed for the regioselective synthesis of 2- and 3-iodoimidazo[1,2-a]pyridines using alkenes/alkynes as coupling partners in the presence of molecular iodine under aerobic reaction conditions. This method was also applied to the synthesis of 2-iodo-3-phenylbenzo[d]imidazo[2,1-b]thiazoles. This protocol offers an easy route towards the synthesis of 2,3-diarylimidazo[1,2-a]pyridines.

Regioselective synthesis of nitrosoimidazoheterocycles using tert-butyl nitrite.

A simple and practical method has been developed for the regioselective nitrosylation of imidazopyridines via C(sp(2))-H bond functionalization using tert-butyl nitrite under mild reaction conditions in a short time. A library of 3-nitrosoimidazopyridines with broad functionalities was synthesized in near quantitative yields. The present protocol is also applicable to imidazo[2,1-b]thiazole and benzo[d]imidazo[2,1-b]thiazole.

Regioselective oxidative trifluoromethylation of imidazoheterocycles via C(sp2)-H bond functionalization.

Catalytic oxidative trifluoromethylation of imidazopyridines has been carried out at room temperature through the functionalization of the sp(2) C-H bond employing Langlois reagent under ambient air. A library of 3-(trifluoromethyl)imidazo[1,2-a]pyridines with broad functionalities have been synthesized regioselectively. This methodology is also applicable to imidazo[2,1-b]thiazole and benzo[d]imidazo[2,1-b]thiazole.

Copper-catalyzed regioselective synthesis of furan via tandem cycloaddition of ketone with an unsaturated carboxylic acid under air.

A catalytic decarboxylative annulation has been developed for the regioselective synthesis of trisubstituted furans by the cycloaddition of ketones with α,ß-unsaturated carboxylic acids under ambient air. A library of furan derivatives were obtained in good yields from the readily available substrates in the combination of a catalytic amount of Cu-salt and a stoichiometric amount of water. Water plays a crucial role in this catalytic transformation.

Synthesis of imidazo[1,2-a]pyridines: a decade update.

Imidazopyridine is one of the important fused bicyclic 5-6 heterocycles and it is recognized as a "drug prejudice" scaffold due to its wide range of applications in medicinal chemistry. This moiety is also useful in material science because of its structural character. Synthesis of this moiety from the easily available chemicals is desirable due to its tremendous use in the various branches of chemistry. Here we report a review on the synthesis of this scaffold employing different strategies such as condensation, multicomponent reactions, oxidative coupling, tandem reactions, aminooxygenation, and hydroamination reactions.

FeCl3/ZnI2-catalyzed synthesis of benzo[d]imidazo[2,1-b]thiazole through aerobic oxidative cyclization between 2-aminobenzothiazole and ketone.

The FeCl3/ZnI2-catalyzed aerobic oxidative cyclization between 2-aminobenzothiazole and ketone/chalcone for the synthesis of benzo[d]imidazo[2,1-b]thiazole is described. A variety of fused benzoimidazothiazole derivatives are obtained by this protocol.

Unprecedented catalytic activity of Fe(NO3)3·9H2O: regioselective synthesis of 2-nitroimidazopyridines via oxidative amination.

A unique iron-catalyzed oxidative diamination of nitroalkene with 2-aminopyridine for the synthesis of 2-nitro-3-arylimidazo[1,2-a]pyridines with complete regioselectivity has been achieved under mild and aerobic reaction conditions. This is the first method for the synthesis of 2-nitroimidazo[1,2-a]pyridines. These scaffolds were also synthesized directly from styrenes.